Make CloudPolicyValidator memory management clearer

components/policy/core/common/cloud/user_cloud_policy_store.cc

Index: components/policy/core/common/cloud/user_cloud_policy_store.cc
diff --git a/components/policy/core/common/cloud/user_cloud_policy_store.cc b/components/policy/core/common/cloud/user_cloud_policy_store.cc
index 9307530d63bf6014d2647a4db46561446c4f8c90..47917bcacfa3ebed28844a1d7027dd63151500a7 100644
--- a/components/policy/core/common/cloud/user_cloud_policy_store.cc
+++ b/components/policy/core/common/cloud/user_cloud_policy_store.cc
@@ -408,9 +408,8 @@ void UserCloudPolicyStore::Validate(
   }
 
   if (validate_in_background) {
-    // Start validation in the background. The Validator will free itself once
-    // validation is complete.
-    validator.release()->StartValidation(callback);
+    // Start validation in the background.
+    UserCloudPolicyValidator::StartValidation(std::move(validator), callback);
   } else {
     // Run validation immediately and invoke the callback with the results.
     validator->RunValidation();